We recently purchased a 10" Dobsonian (Skywatcher from Aus. Geographcic) as a starter telescope. We have taken it out twice. The first time we left the main cover on the scope (only took off the smaller cover), however we were still very impressed looking at the moon.
This morning (4am) we took it out for a second outing to look at some of the planets. The location (front yard) is not ideal as the street lights are annoying, but we are still working out the mechanics of the scope, so that isn't too much of a concern.
However, this time we took off the main cover, it was impressive just how much more we could see... BUT, the cross-hairs (are they called restraints? The bars that hold one of the mirrors near the top of the scope) and the mirror obstructed the view.
What we did see was just white light. Nothing discernible, other than the circular shape of what we were pointing at (in our case we looked at both Venus and Jupiter).
We were definitely pointed at them, as moving away removed the white circle from view. However the circle was ill-defined and nothing on the surface was distinguishable, and as mentioned it was partially obstructed by the restraints and the mirror.
I don't know what to do next. Any help will be much appreciated.
Sounds like it wasn't in focus
With Jupiter you should see a disc with the band's running through and the main moons
Is there an extension tube in the focuser , if so remove it and try again
Hi Cassie, as david said it seems that it was not in focus, a good way to start to get focus right is to place a lower magnification eyepiece in the scope if you have more than one (these are the ones with a higher number on the eyepiece) as you turn the focuser while looking at a bright star you will see the large white circle of light in the eyepiece get smaller untill the star is a bright small pinpoint dot (focused stars should always be just a bright pinpoint dot) now if you point the scope at a planet you will just need a small adjustment to see the planet as a small round ball. To magnify the planet you will need to place a higher magnifing eyepiece in the scope ( these are ones with a lower number on the eyepiece) or place the 2x 3x 5x magnifing barlow lense if you have one, a small adjustment of the focus will make the planet a little larger in the eyepiece.
It sounds like the 'cross-hairs' your seeing maybe the spider vanes that hold the secondary mirror in place. Normally you should not really see them other than their diffraction spikes (sorry for the technical term). It does sound like your out of focus, and assuming the scope is properly assembled it should be able to reach focus. As suggested try a wide field of view eyepiece and don't use any extension tubes, and report back. Allan_l is a good teacher on those scopes, I'd follow his advice too.
The first image is what my setup was (sans eyepiece which is packed away), and if I understand correctly, the second image is what it should be next time?
I have always been a bit confused by the 1.25" and 2" thing. I think I have 1.25" lenses, if so what is that piece that I removed for?
The first image is what my setup was (sans eyepiece which is packed away), and if I understand correctly, the second image is what it should be next time?
I have always been a bit confused by the 1.25" and 2" thing. I think I have 1.25" lenses, if so what is that piece that I removed for?
Yes, Cassie.
This is what I was referring to.
You are now setup for some good viewing.
The other piece (that you removed) is the 2" adapter, and is for when you get (more expensive and bigger) eyepieces which have a 2" barrel.
If you can come along to a viewing night or camp we can let you borrow some to see what sort of difference it makes in your scope.
For now, 1.25" eyepieces are perfectly fine for your viewing pleasure.
The supplied skywatcher eyepieces are pretty good quality for starters.
A second question. I know that it is not okay to stick a telescope out the window, however, given that one of the planets is nicely visible outside of one of my windows, and also given the constraints of a fly-in-fly-out husband, my dislike of being outside alone at 4am by myself, and the early evening hours being occupied by kids bed and bathtime.
Would it be acceptable to setup the telescope out the window while I am figuring all of this stuff out? Really at the moment I am just trying to work out how to use the telescope, and not really caring about image quality.
A second question. I know that it is not okay to stick a telescope out the window, however, given that one of the planets is nicely visible outside of one of my windows, and also given the constraints of a fly-in-fly-out husband, my dislike of being outside alone at 4am by myself, and the early evening hours being occupied by kids bed and bathtime.
Would it be acceptable to setup the telescope out the window while I am figuring all of this stuff out? Really at the moment I am just trying to work out how to use the telescope, and not really caring about image quality.
Out the window is not ideal, but as you say, if you dont have a flyscreen, and can open the window, go for it.
Issues such as thermal currents may degrade the view a little, and with a dob, you may have some problems pointing, but when you are learning to use it, any practice is good practice. And your safety is paramount.
Enjoy.
Thank you for your help. I will have another go tonight and let you know how I go.
@Alan, I just saw that you are from the Central Coast, does that mean you are part of the Newcastle Astronomy Group? I found them on facebook, and am hoping to get along to a few events next year.
10" Dobs are generally Rich Field Telescopes. Rich Field Telescope are generally an F/4 Focal Ratio or less. They have a very wide field of View, and provide bright images. If the magnification of the eyepiece is too low, part of the Secondary Mirror will be seen as a dark spot through the eyepiece.
Low magnification of the Planets, especially bright Jupiter, will show no detail. You need to have a minimum of around 150x to spread out the light a bit, and show details. Otherwise the planet is just too bright, using your size of telescope.
Although the hole in your Dust Cap is quite small, observing Jupiter using just this small hole will cut down the light considerably. It will also change the focal ratio of the telescope to a longer one (better for planets). It's important to align the hole where the Spider (cross hairs) isn't. Using this method, the Spider and Secondary Mirror are no longer an obstruction to the Main Mirror, since the Main Mirror only sees the light coming through the small Dust Cover hole. The small hole means the Resolution of Telescope is reduced. This reduces the quality of the clarity of the image. So it's a case of getting the right size hole to suit your type of Telescope. Use a piece of cardboard, instead of the Dust Cap, with a larger circle cut out of it. The circle can be oval shaped, to be larger, and better fit the gap between the Spider Vanes, as long as the shape is curved, it won't bother the optics. You can cut more than one circle, to fit between the Spider Vanes. If you cut 2 circles, opposite each other - hey, you've made a Hartmann Mask! Used for getting perfect focus. Just adjust the Focuser until the 2 images of Jupiter become one.
Oh, using a telescope through a flyscreen is fine. The flyscreen is so far out of focus it won't bother the image. The flyscreen will drop the brightness of the image by the amount the flyscreen blocks out the light from the Main Mirror. Windows are not optically flat, so they distort the image.
Oh! Cross Hairs are the hairs that cross in your finder scope, since they were originally, and still are sometimes made from hair.
Allan, I just saw that you are from the Central Coast, does that mean you are part of the Newcastle Astronomy Group? I found them on facebook, and am hoping to get along to a few events next year.
No. I am part of an informal group on the Central Coast.
(No memberships, no fees, no politics.)
You are welcome to join us for observation sessions etc.
But there are a few from IIS who are Newcastle Astronomy Group members.
H0ughy may be able to fill you in better, I believe he is or was involved with them. http://www.iceinspace.com.au/forum/member.php?u=221
Thank you all for your help. I poked it out the window today and had a look at the moon (7ish at night, so still very bright). However the problem is nicely sorted, I will set my alarm for the early hours of the morning and head outside for a better look.
Thank you all.
(The photo is taken using my iPhone, the sun was still up, and the telescope was pointed through a window, and the kids kept shaking the floor.... Ideal conditions!! )
(The photo is taken using my iPhone, the sun was still up, and the telescope was pointed through a window, and the kids kept shaking the floor.... Ideal conditions!! )
You gotta be happy with that shot.
A good bit of detail is clear, especially along the terminator (that line on the moon where light meets dark)
Very happy with it. Thank you again for your help.
I took another look (same window) at about 11pm last night. I saw my first galaxy which was pretty exciting. I tried to figure out which one it was but I couldn't figure out how to use my planisphere or the book that came with it, and the app (starwalk2) shows confusing amounts of detail.
It looked like a wolf (I thought) with a cluster of 4 stars in one eye (at first I thought I had the telescope badly out of focus).
I plan to have another look tonight and see if I can figure out what I was looking at. It was pretty exciting to stumble across.
I also happened to wake about 2am (and Jupiter was conveniently out the same window) so I took another look. I am certain I was looking at Jupiter (it was extremely bright and the shape was well defined), however I didn't see anything more than a bright white circle. There were smaller circles near it, but they were far enough away that I think they were just other stars.
All in all I am very happy with it set up out the loungeroom window (I mean, for a week or so while I get the hang of it). It is getting used, I have stuff spread out all over the coffee table, and a comfy seat while I try to figure the planisphere out, and best - if a child wakes (which one did), it was nothing to walk to the next room and settle her before returning to the telescope (if it was outside I would have abandoned the exercise and brought it all in).
I mean, I do realise the image quality is not great, and obviously I have a limited angle of view... but as an initial setup for a week while I am learning how to use the tools... I would highly recommend it.
The Great Nebula in Orion, M42 is what you are looking at there. Have alook in Images, DSO section to find an astrophoto that shows you more details.
Yep upside down and back to front, it's the result of simplified optics. The less glass ( lenses) and mirrors you have in an optics train the less chance of distortion or light loss and simpler to collimate. You get used to it after a while.
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